{
  "bibcode": "1998GCN...182....1B",
  "body": "GRB 981226: Optical Observations\n\nJ. S. Bloom, R. R. Gal, and J. Meltzer (Caltech), on behalf of the\nCaltech/NRAO GRB collaboration, report:\n\n\"On 27.1 and 28.1 December 1998 UT we obtained optical images of the X-ray\nlocalization (GCN #174; GCN #178) of GRB 981226 at the Palomar 60-inch.\nTotal integration time was 1800-s and 3450-s with an approximate gunn-i\nobject detection threshold of 23.5 and 24.3 (on 27.1 Dec, 28.1 Dec,\nrespectively).  An astrometric plate solution was obtained by comparing\nfield stars to that from USNO-A2 Catalogue; the rms fit in either axes was\nfound to be 0.18 arcsec.  We assumed the standard zero-point for the\ninstrument; for comparison, this zero-point gives gunn-i = 20.47 for the\nstar at ra: 23:29:43.5, dec: -23:54:13.8 (J2000).\n\nThe J-band source reported by Castro-Tirado et al. (GCN #173) is not\ndetected at either epoch, implying a J - i of greater than about 3.5 mag\non 27.1 Dec UT.  The source reported by Galama et al. (GCN #172) did not\nvary significantly (delta m = 0.12 mag, consistent within the photometric\nerror of r.m.s. = 0.1 mag) and is not likely to be the optical transient\nof this GRB.  These statements are consistent with those by Rhoads et al.\n(GCN #181).\n \nWe do find that the object at ra: 23:29:27.33, dec: -23:56:53.7 (+/- 0.18\narcsec), reported as possibly variable by Wozniak (GCN #177), to have\nfaded by 0.46 (+/- 0.09 rms) mag between the two epochs.  Our preliminary\nphotometry gives i=22.9 +/- 0.2 and i=23.4 +/- 0.2 on the first and second\nepochs, respectively.  We note that this source is well-outside (~1.5\narcmin) the formal error box of the X-ray NFI position (GCN #178), so its\nconnection with GRB 981226 remains to be established.  If indeed this\nsource is the transient afterglow of the GRB, then the measured time decay\nconstant is alpha = -0.5; this is shallower than those found in other\nafterglow but can be reconciled if the underlying galaxy host is of\ncomparable brightness to the transient.\n\nThis message may be cited.",
  "circularId": 182,
  "createdOn": 915001369000,
  "email": "jsb@astro.caltech.edu",
  "subject": "GRB 981226",
  "submitter": "Josh Bloom at CIT  <jsb@astro.caltech.edu>",
  "eventId": "GRB 981226"
}